1. Field of the Invention
The present invention relates to the field of telecommunications. More particularly, the invention is concerned with a telecommunications network using data packets for signaling among network components, such as signal transfer points, switches, service control points, and adjunct processors, in which signaling packets are transferred to the network for transmission to a destination component only if that signaling packet is different from the previous packet sent to the same destination. The signaling packets are transferred over respective virtual channels assigned to respective pairs of network components.
2. Description of the Prior Art
In the prior art, signaling systems such as Signaling System #7 (SS#7) use continuous streams of successive data packets for signaling between network components such as switches, signal transfer points, and adjunct processors. In a typical arrangement, each switch in a network is linked to one or more signal transfer points (STPs) for signaling. The STPs route the signaling packets for the switches and for other network components. These components include service control points and connections with other carriers including both interexchange carriers and local exchange carriers.
In a typical arrangement, two signaling links making up a linkset are provided between each switch and a signal transfer point with each link consisting of a DSO channel. Two links are provided for redundancy and traffic is purposefully limited so that either link may carry the entire load if the other fails. Network components often divide the traffic equally between companion links.
In the SS#7 environment, a continuous stream of successive signaling packets are generated and sent between interconnected components. These packets include message signal units (MSU), fill-in signal units (FISU) and link status signal units (LSSU). An MSU contains the message for the destination and is the means by which signaling is accomplished within the network. FISUs are used to fill idle time between MSUs on the signaling link and are also important for message sequence control. LSSUs are used for management and control of the associated link. On a given signaling link, MSU loading is typically limited to a maximum of about 35% for steady state operation with the remaining 65% of the link bandwidth being typically occupied by the fill-in units (FISUs). Generally, the LSSUs occupy a negligible percentage of bandwidth.
As network demands increase, signaling capacity must increase also. This can be accomplished by adding additional links, which are added in powers of two in order to keep the loading equally divided. In other words, the allowable number of links between a switch and an STP can include two, four, eight and so forth. As those skilled in the art will appreciate, this can be expensive and presents a substantial waste of bandwidth because typically at least 65% of the capacity is used to carry fill-in units (FISUs).
Additional link capacity can be accomplished by using DS1 channels instead of DS0 channels, for example. However, this represents a similar or even greater waste of bandwidth.
The prior art architecture for signaling presents an additional problem because all of the signaling among the switches is routed through the STPs. An operational failure of a single STP or STP pair can adversely affect the entire network.
Ideally, a network would be configured for associated signaling so that each network component has a dedicated signaling channel with every other component in the network. This would greatly enhance survivability and robustness of network signaling. At present, such an architecture is impractical, however, because the number of linksets would increase geometrically with the number of connected components and the expense would be prohibitive.
There are packet or other data technologies available that would allow a signaling network architecture to be made up of direct virtual links between each pair of network components. Problems still exist however, in that the continuous stream of packets generated by the SS#7 environment would continually load the virtual links, and in reality, convert them into dedicated links requiring extensive bandwidth.
There are also packet or other data technologies available that can be used to reduce the load on a virtual link. One such technology suppresses redundant packets at the transmitting end and regenerates these packets at the receiving end. At present, packet transmission using virtual channels and employing packet suppression has not been applied to large telecommunications network signaling systems, and as a result, there is a still a need for a bandwidth on demand signaling system.